The present invention relates generally to an improved electrophotographic copying apparatus which utilizes a roll packaged type of copying paper and which has an adjustable magnification for reproducing copies of different magnification ratios, and more particularly it relates to an improved electrophotographic copying apparatus which permits the cutting of the copying paper into the length of the reproduced image regardless of the copying magnification ratio at which the image is formed.
A conventional type of electrophotographic copying apparatus employs what is known as a random cutting mechanism for cutting the copying paper withdrawn from a roll thereof to the length of an original to be copied. Such apparatuses are described in U.S. Pat. No. 3,651,727 and No. 3,614,220 in which the copying apparatuses shown in both of these patents are of the slit exposure type with the apparatus of the former patent performing the scanning of the original by the movement of optical means and the apparatus of the latter patent by the movement of the original holder. In both apparatuses, the original to be copied is placed on an original holder with an end aligned with a reference edge and then a slidable indicator member is moved along the original to align it with the other end of the original. By this alignment, means associated with the indicator member is adjusted to cut the copying paper into the length of the original so that upon operation of the copying apparatus, said means actuates a switch means to energize a cutter to cut the copy paper. Normally, such means is provided on the original holder or optical element for utilizing the scanning movements of either to actuate the cutter.
Furthermore, there has been proposed in recent years a copying apparatus with a magnification adjustment means which permits the reproductions of images at different copying or magnification ratios such as at normal 1:1 and at reduced 1:0.708 copying ratios.
In this type of electrophotographic copying apparatus such as that described in U.S. Pat. No. 3,614,222, the scanning speed for the original to be copied is retained at the same speed as the rotating speed of the photosensitive member onto which the image of the original is projected when obtaining a copy at a 1:1 copying ratio. On the other hand, if the n th power magnification of the reproduction image is desired, the scanning speed of the original must be changed to 1/n th if the rotating speed of the photosensitive member is maintained constant.
In addition to the above change which requires the change in scanning speed, the optical length between the original and the photosensitive must be corrected. This is accomplished as described in U.S. Pat. No. 3,614,222 by shifting part of the optical system which includes first and second optical carriages movable at a speed ratio of 1:0.5 parallel to the original and a projection lens. Specifically, the second carriage and the lens are shifted to compensate the optical length when obtaining a copy at a different copying or magnification ratio.
In the above type of copier, the image of the original is scanned by the first carriage and then reflected to the second carriage moving at half the speed of the first carriage and projected onto the photosensitive member through the lens. Conventionally, the image forming steps such as charging and exposure are normally conducted by means actuated by the copying paper as it is transported or by switch timing cam means driven at a related speed with respect to the scanning speed to actuate the charging and exposure means. In this case, the moving speed of the photosensitive member, the feeding speed of the copying paper and the driven speed of the cam means normally remain the same regardless of the magnification copying ratio and accordingly, the timing at which the charging and exposure means are actuated and the timing at which the scanning means pass through the reference point of the original would become different. This, in other words, will result in the failure in coincidence of the leading end of the original with the leading end of the copying paper, that is, the image will not be properly formed on the copying paper. A similar problem is encountered in a copier with magnification means in which the original holder scans with the optical means being stationary.
Accordingly, if the random cutting mechanisms such as those disclosed in U.S. Pat. No. 3,651,727 and No. 3,614,220 are utilized in the afore-described copiers, the problems are encountered that not only that the copying paper cannot be cut into the size of the original but also the copying paper is not cut into the length of the reproduced image if copies at different copying ratios are to be obtained. This is true even if the means for correcting the timing of the paper feed is provided since the scanning speed for the original would vary in accordance with the magnification power at which the copying is performed. Thus, there has not been conventionally available in a photocopying machine of the above types a roll paper cutting device which cuts the copying paper into a size of image formed thereon when copying at other than a 1:1 copying ratio.